you won't want to use the tub. i screwed up one of my grows by using that exact thing you have. get a 10 gallon rubbermaid and 2 big netpots and use can use all your other equipment that you have. you will not be able to grow plants in those little cups. you can try and try and keep them small, but they still get too big to manage for those little cups. They fall all over the place and it doesn't work at all.